#!/usr/bin/python
import os, sys, socket, syslog
from time import sleep
from glob import iglob
from datetime import datetime
import argparse
import pickle, struct
import pyinotify

sock = socket.socket()
last_timestamp = 0

# This file could not be formatted by Black.

def logging(message, level = syslog.LOG_INFO):
    syslog.syslog(level, message)
    #print message


def read_vpn_acct_file(filename):
    logging("Reading file %s..." % (filename, ), syslog.LOG_DEBUG)

    tstamp = 0
    with open(filename) as f:
        data = []
        for line in f:
            if line.startswith('# time:'):
                tstamp = int(line.split(':')[1].strip())
            elif line.startswith('#'):
                pass
            else:
                data.append(line.split())

    metrics = []
    for d in data:
        # format: username ip qos uptxbytes downrxbytes
        if len(d) == 5:
            metrics.extend([
                ('%s.%s.uptxbytes' %
                (options.prefix, d[0]), (tstamp, int(d[3]))),
                ('%s.%s.downrxbytes' %
                (options.prefix, d[0]), (tstamp, int(d[4]))),
            ])
    return tstamp, metrics


def send_to_carbon(metrics):
    # http://graphite.readthedocs.org/en/latest/feeding-carbon.html
    logging("Sending %d metrics..." % len(metrics), syslog.LOG_DEBUG)
    payload = pickle.dumps(metrics)
    header = struct.pack("!L", len(payload))
    message = header + payload
    sock.sendall(message)
    

def process_vpn_file(filename, old_tstamp = 0):
    logging("Processing VPN file %s..." % (filename,), syslog.LOG_DEBUG)

    global last_timestamp
    tstamp, metrics = read_vpn_acct_file(filename)

    if tstamp >= old_tstamp:
        try:
            send_to_carbon(metrics)
        except socket.error:
            if last_timestamp == 0: # error not detected yet
                last_timestamp = tstamp


def handle_old_vpn_files(directory, old_tstamp):
    # We go back one minute earlier to scan the files. However, we will do an exact
    # comparison when handling the matching files (see process_vpn_file() function).
    
    old_date = datetime.fromtimestamp(old_tstamp-60)
    logging(
        "Starting processing deferred files starting at %s..." %
        (old_date.strftime('%Y%m%d%H%M%S'),),
        syslog.LOG_DEBUG
    )
    for f in iglob(directory + '/*'):
        try:
            tmp_tstamp = datetime.strptime(
                os.path.basename(f).split('-')[0],
                '%Y%m%d%H%M%S'
            )
        except ValueError:
            # Bad filename format: likely not an accounting file...
            pass
        else:
            if tmp_tstamp > old_date:
                logging(
                    "Processing deferred file %s..." % (f,),
                    syslog.LOG_DEBUG
                )
                process_vpn_file(f, old_tstamp)


class VPNAcctHandler(pyinotify.ProcessEvent):
    def process_IN_MOVED_TO(self, event):
        self.handle_file(event)

    def process_IN_CLOSE_WRITE(self, event):
        self.handle_file(event)

    def handle_file(self, event):
        logging(
            "Event detected for file %s..." % (event.pathname,),
            syslog.LOG_DEBUG
        )

        if last_timestamp > 0:
            # Error ongoing: will wait till the connection is back (and last_timestamp == 0)
            logging(
                "Error ongoing: %s will be processed later..." % (event.pathname,),
                syslog.LOG_DEBUG
            )
            return

        process_vpn_file(event.pathname)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        description="Watch for a specific directory containing OpenVPN accounting data " \
                    "and as soon as a new file is created, parse it and send the " \
                    "accounting data to a Carbon daemon.",
        epilog="Send comments/remarks/complaints to <tech@illyse.org>.",
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)

    parser.add_argument('directory', help='directory to watch')
    parser.add_argument('prefix', help='prefix for Graphite metrics')
    parser.add_argument('-t', '--timestamp', dest='tstamp', type=int, default=0, help='Timestamp to recover data from')
    parser.add_argument('-s', '--server', dest='server', default='localhost', help='Carbon daemon address')
    parser.add_argument('-p', '--port', dest='port', type=int, default=2004, help='Carbon daemon port')
    options = parser.parse_args()

    logging(
        "Connecting to Carbon agent on %(server)s on port %(port)d..." %
        {"server": options.server, "port": options.port},
        syslog.LOG_DEBUG
    )
    try:
        sock = socket.create_connection( (options.server, options.port) )
    except socket.error:
        logging(
            "Couldn't connect to %(server)s on port %(port)d, is Carbon agent running?" %
            {"server": options.server, "port": options.port},
            syslog.LOG_ERR
        )
        sys.exit(1)

    if options.tstamp > 0:
        handle_old_vpn_files(options.directory, options.tstamp)
    
    last_timestamp = 0
    
    def on_loop(notifier):
        """
        Function called after each event loop to handle connexion errors.
        """
        global last_timestamp, sock

        if last_timestamp > 0:
            sock.close()
            try:
                sock = socket.create_connection((options.server, options.port))
            except socket.error:
                logging(
                    "Couldn't connect to %(server)s on port %(port)d, is Carbon agent running?" %
                    {"server": options.server, "port": options.port},
                    syslog.LOG_ERR
                )
            else:
                handle_old_vpn_files(options.directory, last_timestamp)
                last_timestamp = 0

    # https://github.com/seb-m/pyinotify/blob/master/python2/examples/daemon.py
    logging("Starting to watch %s directory..." % (options.directory,))
    wm = pyinotify.WatchManager()
    handler = VPNAcctHandler()
    notifier = pyinotify.Notifier(wm, handler)
    wm.add_watch(
        options.directory,
        pyinotify.IN_CLOSE_WRITE | pyinotify.IN_MOVED_TO
    )

    try:
        notifier.loop(
            daemonize=True,
            callback=on_loop,
            pid_file="/var/run/pyinotify.pid",
            stdout="/var/log/pyinotify.log"
        )
    except pyinotify.NotifierError, err:
        print >> sys.stderr, err